JP2018144495A - Ink jet recording method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide: an ink jet recording method in which when one-pass printing recording is performed, the bleeding among color inks is suppressed and the bleed-through of the inks in the recording medium can be prevented; and an ink set suitable for the ink jet recording method.SOLUTION: In an ink jet recording method, one-pass printing recording is performed by using two or more inks; static surface tension differences between the two or more inks are all 2 mN/m or lower; and the ink having the lowest Lvalue is printed first, and the ink having the highest Lvalue is printed last.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an ink jet recording method and an ink set suitable for the ink jet recording method.

  An ink jet printer is known as one of printing apparatuses that form an image by ejecting ink onto a recording medium. Among ink jet printers, line type printers are used as printers capable of high-speed printing. In a line-type printer, one or a plurality of print heads (hereinafter also referred to as “line heads”) that realize a nozzle row having a length corresponding to the length of the recording medium in the width direction (direction perpendicular to the transport direction). The recording medium is conveyed to these line heads, and printing on the recording medium is performed without moving the line head in the direction orthogonal to the conveying direction.

  In a line-type printer having such a configuration, printing is normally performed in one pass without performing overprinting twice or more. Therefore, in order to ensure solid filling, it is necessary to increase the ink weight of one dot. I don't get it. If it does so, the subject that the bleed phenomenon between inks will occur easily occurred.

  As means for solving such a problem, there are two types in which the dynamic surface tension of each ink used in the line type printer is 37 to 48 mN / m, and the difference in the dynamic surface tension is all 2 mN / m or more. There has been proposed an image recording method for forming an image by ejecting the above inks in order from an ink having a large dynamic surface tension (see Patent Document 1).

JP 2013-107224 A

  However, the technique described in Patent Document 1 has a problem in that although bleed is suppressed between black and color, bleed is greatly generated between colors. This is because black bleed does not allow black ink to bleed into color ink (that is, color ink may bleed into black ink), but bleed between colors must not bleed between inks of at least three colors. .

  Also, in a line-type printer, since the ink weight of one dot must be increased in order to ensure solid filling, the ink in which only the dynamic surface tension is controlled, such as the ink disclosed in Patent Document 1. In some cases, ink breakthrough may occur in the recording medium. In the present specification, “ink back-through” refers to a state where ink has penetrated to the back side of the recording medium.

  After the ink droplets land on the recording medium and reach an equilibrium state, it is considered that the static surface tension becomes more dominant than the dynamic surface tension of the ink. That is, before the ink droplet reaches the equilibrium state, the dynamic surface tension becomes dominant because the amphiphilic substance such as the surfactant is not regularly oriented at the gas-liquid interface of the ink droplet. On the other hand, after the ink droplet reaches an equilibrium state, the amphiphilic substance is regularly oriented at the gas-liquid interface of the ink droplet, so that the static surface tension becomes dominant.

  One aspect of the present invention solves at least a part of the above-described problems, thereby suppressing the occurrence of bleeding between color inks and performing backside ink in a recording medium when performing one-pass printing recording. It is an object of the present invention to provide an ink jet recording method capable of preventing omission and an ink set suitable for the ink jet recording method.

  SUMMARY An advantage of some aspects of the invention is to solve at least a part of the problems described above, and the invention can be implemented as the following aspects or application examples.

[Application Example 1]
One aspect of the inkjet recording method according to the present invention is:
An ink jet recording method for performing one-pass printing using two or more inks,
The static surface tension differences of the two or more inks are all 2 mN / m or less,
First printed lowest ink L ^* value, characterized by printing the highest ink last L ^* value.

As described above, after the ink droplets land on the recording medium and reach an equilibrium state, the amphiphilic substance is oriented at the gas-liquid interface of the ink droplets, so that the static surface tension is higher than the dynamic surface tension. Becomes more dominant. Therefore, by setting all the static surface tension differences of each ink to be used to 2 mN / m or less, printing the ink with the lowest L ^* value first, and finally printing the ink with the highest L ^* value, In particular, it is possible to suppress the occurrence of bleeding and aggregation between colors and to realize high image quality of colors. Further, if all the static surface tension differences of the inks used are 2 mN / m or less, it is possible to prevent the ink from passing through.

[Application Example 2]
In the inkjet recording method of Application Example 1,
Each of the two or more inks may have a dynamic surface tension of 37 to 48 mN / m when the surface life is 10 ms.

  According to the ink jet recording method of the application example 2, it is difficult to generate disturbance (satellite) of a formed image due to separation between ink droplet ejection and landing on a recording medium.

[Application Example 3]
In the inkjet recording method of Application Example 1 or Application Example 2,
Each of the two or more inks may contain an ethylene oxide adduct of acetylene glycol and 2,4-diethyl-1,5-pentanediol.

  According to the ink jet recording method of Application Example 3, by adding the ethylene oxide adduct of acetylene glycol and 2,4-diethyl-1,5-pentanediol, the static surface tension difference of each ink is all 2 mN / m. It becomes easy to arrange the following, and particularly color bleed can be effectively suppressed. Further, by adding these components, it is possible to effectively prevent the ink from passing through.

[Application Example 4]
In the inkjet recording method of any one of Application Examples 1 to 3,
Each of the two or more inks contains a diol solvent,
The content of the diol-based solvent may be towards the highest ink L ^* value is more than the lowest ink L ^* value.

By adding a diol solvent to the ink, the dynamic surface tension of the ink can be lowered. Immediately after the ink droplets have landed on the recording medium, the dynamic surface tension is still more dominant than the static surface tension. If printing is performed in descending order of the dynamic surface tension, bleeding and aggregation between black and color and between colors can be effectively suppressed. Therefore, by adding a diol solvent, the dynamic surface tension of the ink with the lowest L ^* value that is printed first is higher than that of the ink with the highest L ^* value. Can be effectively suppressed.

[Application Example 5]
In the inkjet recording method of any one of Application Examples 1 to 4,
Each of the two or more inks contains an ether solvent,
The content of the ether solvent may be towards the highest ink L ^* value is less than the lowest ink L ^* value.

By adding an ether solvent to the ink, the dynamic surface tension of the ink can be increased. Therefore, as in Application Example 4, by adding an ether solvent, the dynamic surface tension of the ink with the lowest L ^* value printed first is made higher than that of the ink with the highest L ^* value. Thus, the occurrence of bleeding and aggregation between black and color and between colors can be effectively suppressed.

[Application Example 6]
One aspect of the ink set according to the present invention is:
An ink set for use in the inkjet recording method of any one of Application Examples 1 to 5,
With black ink, cyan ink, magenta ink and yellow ink,
The dynamic surface tension when the surface life of each ink is 10 ms is 37 to 48 mN / m, and the static surface tension difference between the inks is all 2 mN / m or less.

  According to the ink set of Application Example 6, in the ink jet recording method that performs one-pass printing recording, it is possible to suppress the occurrence of bleeding and aggregation between colors and to achieve high image quality of colors. In addition, it is possible to prevent ink from passing through.

[Application Example 7]
In the ink set of Application Example 6,
Each of the inks may contain an acetylene glycol ethylene oxide adduct and 2,4-diethyl-1,5-pentanediol.

  According to the ink set of Application Example 7, by adding the ethylene oxide adduct of acetylene glycol and 2,4-diethyl-1,5-pentanediol, the static surface tension difference of each ink is all 2 mN / m or less. And color bleed in particular can be effectively suppressed. In addition, the ink can be effectively prevented from falling through.

[Application Example 8]
In the ink set of Application Example 6 or Application Example 7,
Each ink contains a diol solvent,
The content of the diol solvent can be greater in the yellow ink than in the black ink.

By adding a diol solvent to the ink, the dynamic surface tension of the ink can be lowered. Immediately after the ink droplets have landed on the recording medium, the dynamic surface tension is still more dominant than the static surface tension. If printing is performed in descending order of the dynamic surface tension, the occurrence of bleeding and aggregation between colors can be effectively suppressed. Therefore, by adding a diol solvent, the dynamic surface tension of the black ink with the lowest L ^* value printed first is made higher than that of the yellow ink with the highest L ^* value, so The occurrence of bleeding and aggregation between the colors can be effectively suppressed.

[Application Example 9]
In the ink set of any one of Application Example 6 to Application Example 8,
Each of the inks contains an ether solvent,
The content of the ether solvent can be less in the yellow ink than in the black ink.

By adding an ether solvent to the ink, the dynamic surface tension of the ink can be increased. Therefore, as in Application Example 8, by adding an ether solvent, the dynamic surface tension of the ink with the lowest L ^* value printed first is made higher than that of the ink with the highest L ^* value. Thus, the occurrence of bleeding and aggregation between black and color and between colors can be effectively suppressed.

FIG. 3 is an explanatory diagram schematically illustrating a configuration of an ink jet recording apparatus including a line head. The top view which shows the structure of a line head typically.

  Hereinafter, preferred embodiments of the present invention will be described. The embodiment described below describes an example of the present invention. In addition, the present invention is not limited to the following embodiments, and includes various modifications that are implemented within a range that does not change the gist of the present invention.

1. Inkjet recording method The inkjet recording method according to the present embodiment is an inkjet recording method in which one-pass printing recording is performed using two or more types of inks, without performing overprinting twice or more with the same ink. Te, static surface tension difference between the two or more ink are all less 2 mN / m, printing the lowest ink initially L ^* value, to print the highest ink last L ^* value Features. Hereinafter, the features of the ink jet recording apparatus, the ink set, and the ink jet recording method used in the ink jet recording method according to the present embodiment will be described.

1.1. Inkjet recording apparatus The inkjet recording apparatus used in the inkjet recording method according to the present embodiment can perform one-pass printing recording with the same ink, particularly without performing two or more overlapping printings. For example, a line head type ink jet recording apparatus can be used.

  Hereinafter, an example of an ink jet recording apparatus including a line head will be described with reference to the drawings. FIG. 1 is an explanatory diagram schematically showing the configuration of an ink jet recording apparatus provided with a line head.

As shown in FIG. 1, the inkjet recording apparatus 10 transports the recording paper 11 by a transport roller 13 that transports the recording paper 11 onto the platen 12, a step motor 14 that rotationally drives the transport roller 13, and a guide rail 15. A line head 20 that ejects ink droplets onto a recording sheet 11 that is mounted and transported in a direction perpendicular to the direction (the arrow direction in FIG. 1), and a line head that is perpendicular to the transport direction of the recording sheet 11 20 includes a vibration element (not shown) that vibrates 20, an ink cartridge 35, and a controller 40 that controls the entire apparatus.

  The vibration element is formed of, for example, a piezoelectric element (electrostrictive vibrator) such as PZT, and is attached to the line head 20. Therefore, by vibrating the vibration element, the line head 20 can be vibrated in the direction perpendicular to the conveyance direction of the recording paper 11 along the guide rail 15.

  The controller 40 is configured as a microprocessor centered on the CPU 41. In addition to the CPU 41, a ROM 42 for storing various processing programs, a RAM 43 for temporarily storing data, and a flash memory 44 capable of writing and erasing data. And an interface (I / F) 45 for exchanging information with an external device, and an input / output port (not shown).

  The RAM 43 is provided with a print buffer area, and print data received from the user PC 46 via the interface (I / F) 45 can be stored in the print buffer area. Various operation signals from the operation panel 47 are input to the controller 40 via an input port. From the controller 40, a drive signal to the line head 20, a drive signal to the step motor 14, and the operation panel 47 are input. Output signals are output through the output port.

  The operation panel 47 is a device for inputting various instructions from the user and displaying and outputting the state. Although not shown, the operation panel 47 is a display or a user that displays characters, figures, or symbols corresponding to the various instructions. Are provided with buttons for performing various operations.

  FIG. 2 is a plan view schematically showing the structure of the line head. As shown in FIG. 2, the line head 20 includes nozzle rows 21a, 21b, 21c, and 21d in which a plurality of nozzles are arranged in a direction orthogonal to the paper conveyance direction, and recording that is greater than the width of the recording paper 11 being conveyed. It has an area, so that one line of images can be recorded collectively on the recording paper 11 being conveyed.

  As the ink ejection method of the line head 20, in the example of FIG. 1, a method of ejecting ink droplets using a pressure generated in the ink pressure chamber of the line head using a vibration element (not shown) is employed. However, the present invention is not limited to this, and various methods such as a thermal ink jet method in which bubbles are generated by a heating element and ink is ejected under pressure can be applied.

In the inkjet recording apparatus 10, an image is formed on a recording medium using the nozzle rows 21 a, 21 b, 21 c, and 21 d in order. In the ink jet recording method according to the present embodiment, it is necessary to print the ink with the lowest L ^* value first, and finally print the ink with the highest L ^* value. The ink with the lowest L ^* value is ejected from the nozzle row 21d, and the ink with the highest L ^* value is ejected from the nozzle row 21d on the most downstream side.

Further, L ^* 2-th lower ink nozzle row 21b value, the ink third lowest L ^* value by the nozzle rows 21c, more is configured to be disposed in this order from the upstream side from the lower ink having L ^* values preferable. By adopting such a configuration, it is possible to effectively suppress the occurrence of bleeding and aggregation between colors and to realize high image quality of colors.

1.2. Ink Set In the ink jet recording method according to the present embodiment, two or more kinds of inks are used. In this specification, a combination of two or more inks is referred to as an ink set. The number of inks is not particularly limited as long as it is two or more, but includes at least four inks of black ink, cyan ink, magenta ink, and yellow ink in that the color gamut (gamut volume) that can be expressed can be expanded. It is preferable to use an ink set.

  Each of these inks contains at least a pigment, a water-soluble organic solvent, and water. Moreover, you may add surfactant, a resin emulsion, a pH adjuster, and another additive to these inks as needed. Hereinafter, each component contained in the ink will be described.

<Pigment>
Each ink constituting the ink set according to the present embodiment contains a pigment. The pigment species is not particularly limited, and various pigments exemplified below can be used.

  Examples of pigments that can be contained in the yellow ink include C.I. I. Pigment Yellow 1, 3, 12, 13, 14, 17, 24, 34, 35, 37, 42, 53, 55, 74, 81, 83, 95, 97, 98, 100, 101, 104, 108, 109, 110, 117, 120, 128, 138, 150, 153, 155, 174, 180, 198 and the like.

  Examples of pigments that can be contained in the magenta ink include C.I. I. Pigment Red 1,3,5,8,9,16,17,19,22,38,48: 3,57: 1,90,112,122,123,127,146,184,202,269; I. Pigment Violet 1,3,5: 1, 16, 19, 23, 38; I. Pigment violet 19 and C.I. I. Examples thereof include a solid solution with Pigment Red 202.

  Examples of the pigment that can be contained in the cyan ink include C.I. I. Pigment blue 1, 2, 15, 15: 1, 15: 2, 15: 3, 15: 4, 16 and the like.

  Examples of the pigment that can be contained in the black ink include C.I. I. And CI pigment black 4,7.

  Specific examples of pigments having other hues include C.I. I. Pigment Orange 34, 36, 43, 61, 63, 71, etc., orange pigments, C.I. I. And green pigments such as CI Pigment Green 7, 10, 36, 37, and 58.

  Each ink constituting the ink set according to the present embodiment can be used as a resin-dispersed pigment in which these pigments are dispersed with a dispersion resin described later. In addition, each ink constituting the ink set according to the present embodiment can use a self-dispersing pigment without using a dispersing resin.

  A self-dispersing pigment refers to a pigment that can be dispersed and / or dissolved in an aqueous medium without a dispersant. Here, “dispersed and / or dissolved in an aqueous medium without a dispersing agent” means that the surface is stably present in the aqueous medium due to the hydrophilic group on the surface without using a dispersing agent for dispersing the pigment. The state that is.

  An ink containing a self-dispersing pigment as a colorant does not need to contain a dispersion resin for dispersing a normal pigment. For this reason, there is almost no foaming due to a decrease in the defoaming property due to the dispersion resin, and it is easy to prepare an ink excellent in ejection stability. In addition, since a significant increase in viscosity due to the dispersion resin can be suppressed, it is possible to contain more pigment, and it is easy to handle such that the print density can be sufficiently increased.

  The self-dispersing pigment is produced, for example, by bonding (grafting) a phosphorus-containing group to the surface of the pigment by subjecting the pigment to a physical treatment or a chemical treatment. Examples of physical treatment include vacuum plasma treatment. Examples of the chemical treatment include a wet oxidation method of oxidizing with an oxidizing agent in water, a method of binding a carboxyl group via a phenyl group by binding p-aminobenzoic acid to the pigment surface, and the like.

  Each ink constituting the ink set according to the present embodiment is preferably a self-dispersing pigment having a phosphorus-containing group via a phenyl group on the pigment surface from the viewpoint of high color developability. As the surface treatment means for bonding the phosphorus-containing group to the pigment surface via a phenyl group, various known surface treatment means can be applied, and sulfanilic acid, p-aminobenzoic acid, 4-aminosalicylic acid and the like are pigments. Examples include a method of bonding a phosphorus-containing group via a phenyl group by bonding to the surface.

  The content of the pigment contained in each ink is preferably 2% by mass or more and 15% by mass or less, and more preferably 4% by mass or more and 9% by mass or less with respect to the total mass of the ink.

<Dispersed resin>
Each ink constituting the ink set according to the present embodiment preferably contains a dispersion resin for dispersing the pigment when a self-dispersing pigment is not used. Although it does not specifically limit as a dispersion resin, It is preferable to contain the dispersion resin of weight average molecular weight 70,000 or more and 100,000 or less and resin acid value of 80 mgKOH / g or more and 120 mgKOH / g or less. By containing such a dispersion resin, the dispersion stability of the pigment in the ink becomes good, and aggregation of the pigment can be suppressed.

  If the weight average molecular weight of the dispersion resin is equal to or more than the lower limit value, the effect of suppressing the pigment from sinking into the paper surface is easily exhibited. If it is below the upper limit, the effect of improving the dispersion stability of the pigment tends to be exhibited. In addition, a weight average molecular weight can be measured by gel permeation chromatography (GPC) using tetrahydrofuran as a solvent, for example, and can be calculated | required by the polystyrene conversion molecular weight.

  In addition, when the resin acid value of the dispersion resin is equal to or higher than the lower limit, the balance between hydrophilicity and hydrophobicity is improved, and the effect of improving the dispersion stability of the pigment is easily exhibited. If it is below the said upper limit, the effect which suppresses that a pigment sinks into the paper surface inside is easy to be expressed.

Examples of such a dispersion resin include polyvinyl alcohols, polyvinyl pyrrolidones, poly (meth) acrylic acid, (meth) acrylic acid-acrylonitrile copolymers, vinyl acetate- (meth) acrylic acid copolymers, vinyl acetate. -(Meth) acrylic acid ester copolymer, (meth) acrylic acid- (meth) acrylic acid ester copolymer, styrene- (meth) acrylic acid copolymer, styrene- (meth) acrylic acid- (meth) acrylic Acid ester copolymer, styrene-α-methylstyrene- (meth) acrylic acid copolymer, styrene-α-methylstyrene- (meth) acrylic acid- (meth) acrylic acid ester copolymer, styrene-maleic acid copolymer Polymer, styrene-maleic anhydride copolymer, vinylnaphthalene- (meth) acrylic acid copolymer, vinylnaphthalene -Maleic acid copolymer, vinyl acetate-maleic acid ester copolymer, vinyl acetate-crotonic acid copolymer, and salts thereof. In the present specification, the description of (meth) acrylic acid indicates acrylic acid or methacrylic acid. As the form of the copolymer, any form of a random copolymer, a block copolymer, an alternating copolymer, and a graft copolymer can be used.

  Examples of the salt include bases such as ammonia, ethylamine, diethylamine, triethylamine, propylamine, isopropylamine, dipropylamine, butylamine, isobutylamine, diethanolamine, triethanolamine, tri-iso-propanolamine, aminomethylpropanol, and morpholine. And a salt with a functional compound.

  The dispersion resin illustrated above may use only one type of the above materials, or may be used in combination of two or more types.

  The content of the dispersion resin contained in each ink is preferably 0.5% by mass or more and 5.0% by mass or less, and 0.8% by mass or more and 3.0% by mass with respect to the total mass of each color ink. The following is more preferable. When the content of the dispersion resin is in the above range, an effect of improving the dispersion stability of the pigment can be sufficiently obtained.

  A method for producing a pigment dispersion containing a pigment and a dispersion resin can be appropriately selected from conventionally known methods. Suitable methods include, for example, media types such as Nano Glen Mill (manufactured by Asada Tekko Co., Ltd.), MSC Mill (manufactured by Mitsui Mining Co., Ltd.), Dino Mill (manufactured by Shinmaru Enterprises Co., Ltd.), and sand mill (manufactured by Yaskawa Seisakusho Co., Ltd.). Examples thereof include a method of obtaining a pigment dispersion by kneading a pigment and a dispersion resin in a suitable liquid medium such as water using a wet disperser. In the processing by the media type wet disperser, beads having a small particle diameter are used. The particle diameter of the beads is not particularly limited, and is typically a particle diameter of 0.5 to 2.0 mm. The material of the beads is not particularly limited, and beads made of a hard material such as zirconia beads or glass beads are used.

<Water>
Each ink constituting the ink set according to the present embodiment contains water as a main solvent. It is preferable to use pure water or ultrapure water such as ion exchange water, ultrafiltration water, reverse osmosis water, or distilled water. In particular, by using water sterilized by ultraviolet irradiation or addition of hydrogen peroxide, the generation of mold and bacteria can be prevented and ink can be stored for a long time. The content of water in each ink is preferably 20% by mass to 70% by mass with respect to the total mass of the ink.

<Water-soluble organic solvent>
Each ink constituting the ink set according to the present embodiment contains a water-soluble organic solvent. As the water-soluble organic solvent, a diol solvent or an ether solvent is preferable because the dynamic surface tension of the ink can be easily adjusted.

  Although it does not specifically limit as a diol type solvent, The thing with the high permeability | transmittance in which a polar group is unevenly distributed like 1, 2- alkanediol is suitable. Examples of such diol solvents include 1,2-hexylene glycol, 1,2-pentanediol, 1,2-hexanediol, 1,2-heptanediol, 1,2-octanediol, 2-ethyl-1 , 3-hexanediol, 2,4-diethyl-1,5-pentanediol, alkanediol having 5 to 9 carbon atoms such as 2-ethyl-2-butyl-1,3-propanediol. These diol solvents may be used alone or in combination of two or more.

By adding a diol solvent to the ink, the dynamic surface tension of the ink can be lowered. Immediately after the ink droplets have landed on the recording medium, the dynamic surface tension is still more dominant than the static surface tension. If printing is performed in descending order of the dynamic surface tension, bleeding and aggregation between black and color and between colors can be effectively suppressed. Therefore, by adding a diol solvent, the dynamic surface tension of the ink with the lowest L ^* value that is printed first is higher than that of the ink with the highest L ^* value. Can be effectively suppressed.

  Of the diol solvents exemplified above, 2,4-diethyl-1,5-pentanediol not only lowers the dynamic surface tension of the ink, but also reduces the static surface tension difference of each ink to 2 mN / m. It becomes easy to arrange the following, and color bleed can be particularly effectively suppressed. Further, by adding 2,4-diethyl-1,5-pentanediol to the ink, the permeability to the recording medium can be controlled, and the ink can be effectively prevented from falling through.

  Examples of ether solvents include ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monopropyl ether, ethylene glycol monobutyl ether, ethylene glycol monomethyl ether acetate, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monopropyl ether, diethylene glycol. Monobutyl ether, diethylene glycol mono-t-butyl ether, triethylene glycol monobutyl ether, 1-methyl-1-methoxybutanol, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol monopropyl ether, propylene glycol monobutyl Ether, dipropylene glycol monomethyl ether, dipropylene glycol monoethyl ether, dipropylene glycol monopropyl ether, dipropylene glycol monobutyl ether, tripropylene glycol monomethyl ether, polyoxyethylene 2-ethylhexyl ether, and the like. These ether solvents may be used individually by 1 type, and may be used in combination of 2 or more type.

By adding an ether solvent to the ink, the dynamic surface tension of the ink can be increased. Therefore, by adding an ether solvent, the dynamic surface tension of the ink with the lowest L ^* value printed first is higher than that of the ink with the highest L ^* value. Bleeding and aggregation can be effectively suppressed.

  Some compounds contain both an ether bond and a diol in the structure. For example, the above-mentioned alkyl ether diol type and the above-mentioned alkylene oxide adduct of acetylene glycol can be used. In the present invention, such a compound is treated as a diol solvent and an ether solvent. That is, when a compound containing both an ether bond and a diol is added, the content is counted as both the content of the diol solvent and the content of the ether solvent.

  It is preferable to adjust the dynamic surface tension to 37 to 48 mN / m when the surface life of each ink is 10 ms by adding a diol solvent or an ether solvent to the ink. By setting the dynamic surface tension of the ink within the above range, it is difficult to cause disturbance (satellite) of a formed image due to separation between ink droplet ejection and landing on a recording medium.

  In the present invention, “dynamic surface tension” refers to surface tension immediately after the liquid surface (gas-liquid interface) is formed and when the liquid surface is in a non-equilibrium state. “Surface life” refers to the elapsed time after the liquid surface is formed. “Static surface tension” refers to the surface tension when the liquid surface approaches the equilibrium state as each component in the ink diffuses as the surface life elapses.

  The method for measuring the dynamic surface tension of the ink can be measured by using a dynamic surface tension meter. Examples of the dynamic surface tension meter include a bubble pressure dynamic surface tension meter (manufactured by KRUSS, model “BP100”).

  The static surface tension of the ink can be measured by an automatic surface tension meter (manufactured by Kyowa Interface Science Co., Ltd., model “DY-300”) using a platinum plate.

  It is also preferable to add a water-soluble organic solvent as a moisturizing agent to each ink constituting the ink set according to the present embodiment. Examples of the humectant include glycerin, 2-pyrrolidone, N-methyl-2-pyrrolidone, and γ-butyrolactone. These humectants may be used alone or in combination of two or more. When the ink contains a humectant, the content of the humectant is preferably 5 to 30% by mass and more preferably 12 to 20% by mass with respect to the total mass of the ink.

<Surfactant>
A surfactant is preferably added to each ink constituting the ink set according to the present embodiment. By adding a surfactant, the static surface tension of the ink can be adjusted. In other words, the static surface tension is the surface tension when the liquid surface is in an equilibrium state. In the case of an ink added with a surfactant, the surface activity is exerted on the gas-liquid interface of the ink droplet when the equilibrium state is reached. The agent is regularly oriented. Accordingly, since the effect of the surfactant is dominant in the static surface tension, in order to make the static surface tension of each ink equal to 2 mN / m or less, a surfactant is added to the static surface tension of the ink. It is desirable to align the tension.

  The surfactant is not particularly limited, and any of an anionic surfactant, a cationic surfactant, an amphoteric surfactant, and a nonionic surfactant can be used. Among these, a nonionic surfactant is preferable from the viewpoint of obtaining an ink with less foaming and bubbles. The nonionic surfactant has an action of spreading the ink uniformly on the recording medium. Therefore, when ink jet recording is performed using an ink containing a nonionic surfactant, a high-definition image with little bleeding can be obtained.

  Among the nonionic surfactants, an alkylene oxide adduct of acetylene glycol (hereinafter, the alkylene oxide adduct is also referred to as “AO adduct”) is more preferable. Since the AO adduct of acetylene glycol has a structure having both a hydroxyl group and an ether group, it is familiar with the above-mentioned diol solvents and ether solvents and does not cause problems as ink physical properties. The HLB value of the AO adduct of acetylene glycol is preferably 10 or more and 15 or less because wettability is further improved.

  Specific examples of the AO adduct of acetylene glycol include, but are not limited to, 2,5-dimethyl-3-hexyne-2,5-diol, 2,5-dimethyl-2,5-hexanediol, 3,6 Examples include those obtained by adding alkylene oxide to acetylene glycol-based diols such as dimethyl-4-octyne-3,6-diol and 2,4,7,9-tetramethyl-5-decyne-4,7-diol. . Specific product names include Surfinol 440 obtained by adding alkylene oxide to Surfinol 104 manufactured by Nissin Chemical Industry Co., Ltd., Surfinol 104A · E · H, Olphine, and the like.

  Surfactant may be used individually by 1 type and may be used in combination of 2 or more type. The content of the surfactant in each ink is preferably 0.5% by mass or more and 5% by mass or less with respect to the total mass of the ink.

  In addition, each ink constituting the ink set according to the present embodiment is obtained by adding an acetylene glycol AO adduct and 2,4-diethyl-1,5-pentanediol, thereby changing the static surface tension difference of each ink. Is preferably adjusted to 2 mN / m or less. By adding these, the difference in static surface tension of each ink can be easily adjusted to 2 mN / m or less, and a preferable ink in which the generation of bubbles and bubbles is suppressed is obtained.

<Resin emulsion>
A resin emulsion may be added to each ink constituting the ink set according to the present embodiment. The resin emulsion has the effect of improving the fixability of the image portion of the recorded matter because the resin particles and the resin particles and the coloring component are fused to each other as the ink is dried to fix the colorant to the recording medium. .

  These resin particles are preferably one or more selected from the group consisting of acrylic resins, methacrylic resins, styrene resins, urethane resins, acrylamide resins, and epoxy resins. These resins may be used as homopolymers or as copolymers.

  As the resin particles, those having a single particle structure may be used, or resin particles having a core / shell structure including a core portion and a shell portion surrounding the core portion may be used. In the present specification, the “core / shell structure” means “a form in which two or more polymers having different compositions are present in phase separation in the particles”. Therefore, the shell portion may not only cover the core portion completely, but may cover a portion of the core portion. Further, a part of the shell polymer may form a domain or the like in the core particle. Further, it may have a multilayer structure of three or more layers including layers having different compositions in the middle between the core portion and the shell portion.

  Such resin particles can be obtained by known emulsion polymerization. That is, it can be obtained by emulsion polymerization of an unsaturated vinyl monomer (unsaturated vinyl monomer) in water in the presence of a polymerization catalyst and an emulsifier.

  Examples of the unsaturated vinyl monomer include acrylic acid esters, methacrylic acid esters, aromatic vinyl compounds, vinyl esters, vinyl cyanide compounds, halogen compounds, olefins, dienes and the like generally used in emulsion polymerization. .

Further, specific examples include methyl acrylate, ethyl acrylate, isopropyl acrylate, n-butyl acrylate, isobutyl acrylate, n-amyl acrylate, isoamyl acrylate, n-hexyl acrylate, 2-ethylhexyl acrylate, octyl acrylate, decyl acrylate, dodecyl acrylate. Acrylates such as octadecyl acrylate, cyclohexyl acrylate, phenyl acrylate, benzyl acrylate, glycidyl acrylate; methyl methacrylate, ethyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, n-amyl methacrylate, isoamyl methacrylate, n-hexyl methacrylate 2-ethyl Methacrylic acid esters such as xyl methacrylate, octyl methacrylate, decyl methacrylate, dodecyl methacrylate, octadecyl methacrylate, cyclohexyl methacrylate, phenyl methacrylate, benzyl methacrylate and glycidyl methacrylate; vinyl esters such as vinyl acetate; vinylcyan compounds such as acrylonitrile and methacrylonitrile; Halogen compounds such as vinylidene chloride and vinyl chloride; aromatic vinyl compounds such as styrene, α-methylstyrene, vinyltoluene, t-butylstyrene, chlorostyrene, vinylanisole and vinylnaphthalene; olefins such as ethylene and propylene, butadiene, Dienes such as chloroprene; vinyl monomers such as vinyl ether, vinyl ketone and vinyl pyrrolidone; Unsaturated carboxylic acids such as crylic acid, methacrylic acid, itaconic acid, fumaric acid, maleic acid; acrylamides such as acrylamide and N, N′-dimethylacrylamide; 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 2-hydroxyethyl Examples thereof include hydroxyl group-containing monomers such as methacrylate and 2-hydroxypropyl methacrylate.

  Moreover, what has the structure bridge | crosslinked by the crosslinkable monomer which has two or more of the polymerizable double bonds can be used for the resin particle as a molecule | numerator derived from the said monomer. Examples of the crosslinkable monomer having two or more polymerizable double bonds include polyethylene glycol diacrylate, triethylene glycol diacrylate, 1,3-butylene glycol diacrylate, 1,6-butylene glycol diacrylate, 1,6-hexanediol diacrylate, neopentyl glycol diacrylate, 1,9-nonanediol diacrylate, polypropylene glycol diacrylate, 2,2′-bis (4-acryloxypropyloxyphenyl) propane, 2,2 ′ Diacrylates such as bis (4-acryloxydiethoxyphenyl) propane; triacrylates such as trimethylolpropane triacrylate, trimethylolethane triacrylate, tetramethylolmethane triacrylate; Tetraacrylates such as roll tetraacrylate, tetramethylolmethane tetraacrylate, pentaerythritol tetraacrylate; hexaacrylates such as dipentaerythritol hexaacrylate; ethylene glycol dimethacrylate, diethylene glycol dimethacrylate, triethylene glycol dimethacrylate, polyethylene glycol dimethacrylate, 1 , 3-butylene glycol dimethacrylate, 1,4-butylene glycol dimethacrylate, 1,6-hexanediol dimethacrylate, neopentyl glycol dimethacrylate, dipropylene glycol dimethacrylate, polypropylene glycol dimethacrylate, polybutylene glycol dimethacrylate, 2 , 2'-bis (4-meta Dimethacrylates such as riloxydiethoxyphenyl) propane; trimethacrylates such as trimethylolpropane trimethacrylate and trimethylolethane trimethacrylate; methylenebisacrylamide; and divinylbenzene. These may be used alone or in combination of two or more. can do.

  Moreover, the polymerization initiator, the emulsifier, and the molecular weight modifier used in the emulsion polymerization can be used according to a conventional method.

  As the polymerization initiator, those used for normal radical polymerization are used, for example, potassium persulfate, ammonium persulfate, hydrogen peroxide, azobisisobutyronitrile, benzoyl peroxide, dibutyl peroxide, Examples include peracetic acid, cumene hydroperoxide, t-butyl hydroxy peroxide, paramentane hydroxy peroxide, and the like. In particular, when the polymerization reaction is performed in water, a water-soluble polymerization initiator is preferable.

  Examples of the emulsifier include sodium lauryl sulfate, those generally used as anionic surfactants, nonionic surfactants, or amphoteric surfactants, and mixtures thereof. These may be used alone or in combination of two or more. Can be used as a mixture.

When the resin particles are produced by emulsion polymerization, particularly when a polymer emulsion composed of anionic resin particles is produced by emulsion polymerization, negative polar groups such as carboxyl groups and sulfonic acid groups are formed on the resin particle surface. Is present, the pH is inclined to the acidic side, and viscosity increases and aggregation tends to occur. Therefore, neutralization with a basic substance is usually performed. As this basic substance, ammonia, organic amines, inorganic hydroxides and the like can be used. Of these, monovalent inorganic hydroxides (potassium hydroxide, sodium hydroxide, lithium hydroxide) are particularly preferred from the viewpoints of long-term storage stability and ejection stability of the polymer emulsion and magenta ink. The addition amount of the neutralizing agent is appropriately determined so that the pH of the polymer emulsion is in the range of 7.5 to 9.5, preferably in the range of 7.5 to 8.5.

  The particle size of the resin particles is preferably in the range of 5 to 400 nm, more preferably in the range of 50 to 200 nm.

  The addition amount of these resin emulsions may be appropriately determined in consideration of fixability and the like, but each ink preferably contains 2% by mass or more in terms of solid content.

<PH adjuster>
It is preferable to add a pH adjuster to each ink constituting the ink set according to the present embodiment. As the pH adjuster, inorganic compounds such as lithium hydroxide, potassium hydroxide and sodium hydroxide; alkanolamines such as ammonia, triethanolamine, tripropanolamine, diethanolamine and monoethanolamine can be used. In particular, it is preferably adjusted to pH 6 to 10 including at least one pH adjusting agent selected from alkali metal hydroxide, ammonia, triethanolamine, and tripropanolamine. If the pH is out of this range, the material constituting the ink jet printer may be adversely affected, and clogging recovery may be deteriorated.

  If necessary, collidine, imidazole, phosphoric acid, 3- (N-morpholino) propanesulfonic acid, tris (hydroxymethyl) aminomethane, boric acid and the like can be used as a pH buffering agent.

<Other additives>
Furthermore, an antifoaming agent, an antioxidant, an ultraviolet absorber, an antiseptic / antifungal agent, and the like can be added to each ink constituting the ink set according to the present embodiment as necessary.

  Antioxidants and ultraviolet absorbers include allophanates such as allophanate and methyl allophanate, biurets such as biuret, dimethylbiuret and tetramethylbiuret, L-ascorbic acid and its salts, etc., Tinuvin 328, 900 manufactured by Ciba Geigy 1130, 384, 292, 123, 144, 622, 770, 292, Irgacor 252, 153, Irganox 1010, 1076, 1035, MD1024, or the like, or a lanthanide oxide or the like is used.

  Examples of the antiseptic / antifungal agent include sodium benzoate, sodium pentachlorophenol, sodium 2-pyridinethiol-1-oxide, sodium sorbate, sodium dehydroacetate, 1,2-dibenzisothiazolin-3-one ( Avecia's Proxel CRL, Proxel BDN, Proxel GXL, Proxel XL-2, Proxel TN) and the like.

1.3. Features of Inkjet Recording Method The inkjet recording method according to the present embodiment is an inkjet recording method in which one-pass printing recording is performed using two or more types of inks, without performing overprinting twice or more with the same ink. a is, the static surface tension difference between the two or more ink is not more than every 2 mN / m, printing the lowest ink initially L ^* value, printing the highest ink last L ^* value It is characterized by that.

The L ^* value in the present invention is a spectrophotometer (manufactured by Hitachi, Ltd., model “U-3000”, cell used: quartz cell having an optical path length of 1 cm, for samples in which each ink is diluted with water and / or acetone. D65 light source with a viewing angle of 2 degrees), and L ^* a ^*
b ^* means a value obtained by calculating the L ^* value (lightness) in the color system.

After the ink droplets land on the recording medium and reach an equilibrium state, the surface active substance is oriented at the gas-liquid interface of the ink droplets, so the static surface tension is more dominant than the dynamic surface tension. . Therefore, by setting all the static surface tension differences of each ink to be used to 2 mN / m or less, printing the ink with the lowest L ^* value first, and finally printing the ink with the highest L ^* value, In particular, it is possible to suppress the occurrence of bleeding and aggregation between colors and to realize high image quality of colors. Further, if all the static surface tension differences of the inks used are 2 mN / m or less, it is possible to prevent the ink from passing through.

In a line head type ink jet recording apparatus, in order to ensure solid filling, the amount of ink per dot must be increased. Therefore, bleeding between color inks is likely to occur, and it is difficult to improve color image quality. Met. Therefore, printing the lowest ink initially L ^* value, and finally by printing the highest ink L ^* value, to suppress the lowest ink L ^* value bleeding highest ink L ^* value It was also found that the occurrence of bleeding between colors can be particularly suppressed by setting the static surface tension difference of each ink to 2 mN / m or less. When two or more inks having a static surface tension difference larger than 2 mN / m are present, bleeding and aggregation occur particularly between colors, and color image quality is liable to deteriorate.

  Moreover, it is preferable that the order of ejecting ink in one pass is ejected in order from the ink having the highest dynamic surface tension. When printing is performed in order of increasing dynamic surface tension, the pigment contained in the ink in the early discharge order is fixed to the surface of the recording medium to some extent, and then the next ink is easily landed on the recording medium. Therefore, the ink in the early discharge order and the ink in the next order are not easily mixed on the surface of the recording medium, and the occurrence of bleeding and aggregation between the colors can be further effectively suppressed.

2. Examples Hereinafter, the embodiments of the present invention will be described more specifically with reference to Examples and Comparative Examples, but the present invention is not limited to these Examples.

2.1. Preparation of pigment dispersion 2.1.1. Production of Self-Dispersing Pigment A process all 4HV mixer (4 liters) was charged with 500 g of pigment, 1 L of ion-exchanged water, and 4-aminophenyl-2-sulfatoethylsulfone (APSES). The resulting mixture was then heated to 60 ° C. with vigorous mixing at 300 rpm for 10 minutes. To this, 20% aqueous sodium nitrite solution (1 equivalent based on the amount of APSES) was added over 15 minutes. Heating and mixing continued for a total of 3 hours.

  The contents of the mixer were taken out by diluting with 750 mL of ion exchange water, and then the resulting dispersion was purified by diafiltration with ion exchange water. At the end of the diafiltration (permeate conductivity <200 microsiemens), the pigment concentration was adjusted to 15% and centrifuged in a Kerr continuous centrifuge (Pilot Huge).

  9.39 g of sodium alendronate ((4-amino-1-hydroxybutane-1,1-diyl) bisphosphonic acid monosodium salt) was then placed in a 2.5 L beaker. To this was added 37.56 g of ion-exchanged water, and then 64.73 g of a 10% aqueous sodium hydroxide solution was added. The mixture was stirred until the solid dissolved. 500 g of dispersion (at 20% solids) was introduced by pumping at approximately 25 mL / min under vigorous stirring. After all of the dispersion was added, the pH was measured to confirm that the pH was above 12.5. Mixing was continued at 70 ° C. for 4 hours.

The dispersion thus obtained was diluted to a solid content of 5%, and diafiltered with ion exchange water until the pH of the permeate was less than 8 (retained after the first diafiltration volume). The liquid was concentrated to 10% solids). The dispersion (adjusted to a solids concentration of approximately 13%) is then sonicated using a Mysonics probe sonicator and centrifuged at 5000G for 10 minutes using a Beckman ultracentrifuge. Thus, large particles were removed to obtain a pigment dispersion described in Table 2. The pigment types used are as follows.
<Pigment type used>
Black pigment dispersion: C.I. I. Pigment Black 4
-Cyan pigment dispersion: C.I. I. Pigment Blue 15: 3
-Magenta pigment dispersion: C.I. I. Pigment Red 122
-Yellow pigment dispersion: C.I. I. Pigment Yellow 74

2.1.2. Manufacture of resin dispersion pigment dispersion 20 parts by mass of organic solvent (methyl ethyl ketone), 0.03 parts by mass of polymerization chain transfer agent (2-mercaptoethanol), polymerization initiator, and each monomer shown in Table 1 are used to sufficiently replace nitrogen gas The polymerization was conducted with stirring at 75 ° C. in the reaction vessel prepared in the above step, and 0.9 mass of 2,2′-azobis (2,4-dimethylvaleronitrile dissolved in 40 mass parts of methyl ethyl ketone with respect to 100 mass parts of the monomer component. Part was added and aged at 80 ° C. for 1 hour to obtain a polymer solution.

  Next, 7.5 parts by mass of the polymer solution obtained above as a solid content is dissolved in 45 parts by mass of methyl ethyl ketone, and a predetermined amount of 20% aqueous sodium hydroxide solution (neutralizing agent) is added thereto to add a salt-forming group. Was further neutralized, and further 20 parts by mass of pigment was added and kneaded in a bead mill for 2 hours. After adding 120 parts by mass of ion-exchanged water to the kneaded product thus obtained and stirring, methyl ethyl ketone was removed at 60 ° C. under reduced pressure, and a part of the water was further removed. A resin-dispersed pigment dispersion was obtained. In addition, about the pigment kind used, it is the same as that of the case of manufacture of said self-dispersion pigment.

2.2. Production of Resin Emulsion 900 g of ion-exchanged water and 1 g of sodium lauryl sulfate were charged into a reaction vessel equipped with a stirrer, a reflux condenser, a dropping device, and a thermometer, and the temperature was raised to 70 ° C. while purging with nitrogen under stirring. Maintaining the internal temperature at 70 ° C., adding 4 g of potassium persulfate as a polymerization initiator, dissolving, and previously stirring 450 g of ion exchange water, 3 g of sodium lauryl sulfate, 20 g of acrylamide, 365 g of styrene, 545 g of butyl acrylate, and 30 g of methacrylic acid The emulsion prepared by adding below was continuously dropped into the reaction solution over 4 hours. After completion of dropping, aging was performed for 3 hours. After cooling the obtained resin emulsion to room temperature, ion exchange water and aqueous sodium hydroxide solution were added to adjust the solid content to 25 mass% and pH 8. The glass transition temperature of the resin particles in the obtained resin emulsion was −6 ° C.

2.3. Preparation of Ink and Ink Set For each color of black, magenta, cyan and yellow, each component shown in Table 2 was mixed and stirred at room temperature for 1 hour, and further filtered through a membrane filter having a pore size of 5 μm to prepare each ink. . In this way, a total of 32 types of black ink (K) A1 to A8, magenta ink (M) A1 to A8, and cyan ink (C) of 8 types of inks with different dynamic surface tension and static surface tension. A1 to A8 and yellow inks (Y) A1 to A8 were obtained. These inks were combined as shown in Table 3 to form ink sets 1 to 8. In addition, the numerical value of Table 2 represents content (mass%) in ink.

  Table 2 below shows the compositions of the inks A1 to A8 used in the ink set described in Table 3. Table 3 below shows ink sets (ink combinations) used in Examples and Comparative Examples. Table 2 also shows values obtained by measuring the dynamic surface tension and static surface tension of the inks A1 to A8. The dynamic surface tension of each ink is a value measured at 20 ° C. using a bubble pressure dynamic surface tension meter (manufactured by KRUSS, model “BP100”). The static surface tension of each ink is a value measured at 20 ° C. using a platinum plate with an automatic surface tension meter (manufactured by Kyowa Interface Science Co., Ltd., model “DY-300”).

In addition, the following were used for the acetylene type surfactant and silicon type surfactant in Table 2, respectively.
Acetylene-based surfactant (manufactured by Air Products, trade name “Surfinol 104PG50”, 2,4,7,9-tetramethyl-5-decyne-4,7-diol)
・ Silicon-based surfactant (BIC Chemie Japan Co., Ltd., trade name “BYK-348”)

2.4. Evaluation Method (1) Bleed Evaluation Two types of recording paper were prepared: plain paper (Xerox 4200 paper) and flyer paper (coated paper for Epson business inkjet printers). Under the ink set and recording conditions shown in Table 4, the heads of the inkjet printer PX-A650 (manufactured by Seiko Epson Corporation) were arranged to form a line head, and the line head printer was modified to print a dedicated output pattern consisting of 400 patches. In this case, the penetration into the background was visually determined based on the following criteria. The results are also shown in Table 4.
A: Very good (no bleeding even when observed with a 30 × microscope)
B: Good (4 point characters can be read)
C: OK (can read 10-point characters)
D: Impossible (10-point characters cannot be read)

(2) Evaluation of strike-through In the same manner as the above bleed evaluation, Xerox 4200 paper was used as recording paper, and 10-point characters were printed on the recording paper with KCMY composite black having a density of 85%. The paper surface obtained by copying the back side of the obtained printed matter with a copying machine was visually determined based on the following criteria. The results are also shown in Table 4.
A: Very good (10-point characters are not copied by back side copy)
B: Good (10-point characters are copied by back side copy but cannot be read)
C: Acceptable (10-point characters are copied and read by back side copy)
D: Impossible (ink oozes out to the back side)

2.5. Evaluation Results Table 4 shows the ink sets, recording conditions, and evaluation test results used in the examples and comparative examples. Details of the recording conditions described in Table 4 are shown in Table 5. In this example and the comparative example, the ink having the lowest L ^* value is the black ink, and the ink having the highest L ^* value is the yellow ink.

  From the results of Table 4, it was found that according to the ink jet recording methods of Examples 1 to 8, the occurrence of bleeding between inks (especially between colors) can be suppressed, and ink breakthrough in the recording medium can be effectively prevented. .

  On the other hand, in the ink jet recording method of Comparative Example 1, since the recording order was yellow ink first and black ink last, occurrence of bleeding and see-through were recognized. Further, in the ink jet recording method of Comparative Example 2, since the static surface tension difference between the black ink and the yellow ink is 2 mN / m or more, bleeding and aggregation occur between the colors, and the color image quality is greatly reduced. Was recognized.

  The present invention is not limited to the embodiments described above, and various modifications are possible. For example, the present invention includes substantially the same configuration (for example, a configuration having the same function, method, and result, or a configuration having the same purpose and effect) as the configuration described in the embodiment. In addition, the invention includes a configuration in which a non-essential part of the configuration described in the embodiment is replaced. In addition, the present invention includes a configuration that achieves the same effect as the configuration described in the embodiment or a configuration that can achieve the same object. In addition, the invention includes a configuration in which a known technique is added to the configuration described in the embodiment.

DESCRIPTION OF SYMBOLS 10 ... Inkjet recording device, 11 ... Recording paper, 12 ... Platen, 13 ... Conveyance roller, 14 ... Step motor, 15 ... Guide rail, 20 ... Line head, 21a, 21b, 21c, 21d ... Nozzle row, 35 ... Ink cartridge , 40 ... Controller, 41 ... CPU, 42 ... ROM, 43 ... RAM, 44 ... Flash memory, 45 ... Interface, 46 ... User PC, 47 ... Operation panel

Claims (9)

An ink jet recording method for performing one-pass printing using two or more inks,
The static surface tension differences of the two or more inks are all 2 mN / m or less,
First printed lowest ink L ^* value, characterized by printing the highest ink last L ^* value, an ink jet recording method.   2. The ink jet recording method according to claim 1, wherein each of the two or more inks has a dynamic surface tension of 37 to 48 mN / m when the surface life is 10 ms.   3. The inkjet according to claim 1, wherein each of the two or more inks contains an ethylene oxide adduct of acetylene glycol and 2,4-diethyl-1,5-pentanediol. Recording method. Each of the two or more inks contains a diol solvent,
The content of the diol-based solvent, towards the highest ink L ^* value is equal to or greater than the lowest ink L ^* value, as claimed in any one of claims 1 to 3 Inkjet recording method. Each of the two or more inks contains an ether solvent,
The content of the ether-based solvent, towards the highest ink L ^* value is equal to or less than the lowest ink L ^* value, as claimed in any one of claims 1 to 4 Inkjet recording method. An ink set for use in the ink jet recording method according to any one of claims 1 to 5,
With black ink, cyan ink, magenta ink and yellow ink,
The dynamic surface tension when the surface life of each ink is 10 ms is 37 to 48 mN / m, and all the static surface tension differences between the inks are 2 mN / m or less. Ink set.   The ink set according to claim 6, wherein each ink contains an ethylene oxide adduct of acetylene glycol and 2,4-diethyl-1,5-pentanediol. Each ink contains a diol solvent,
8. The ink set according to claim 6, wherein the content of the diol-based solvent is higher in the yellow ink than in the black ink. 9. Each of the inks contains an ether solvent,
The ink set according to any one of claims 6 to 8, wherein the content of the ether solvent is smaller in the yellow ink than in the black ink.

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